1. Field of the Invention
The present invention relates generally to ventilators, and more particularly to a manually actuated two-way vehicle ventilator having a cam and follower assembly adapted to limit the opening of the vent.
2. Description of the Prior Art:
Two-way hingeless ventilators of the present type are well known by those of skill in the art, and the operation thereof is described in detail in U.S. patents, particularly U.S. Pat. No. 6,280,315, U.S. Pat. No. 5,766,068, U.S. Pat. No. 4,452,129, and U.S. Pat. No. 3,839,950, the disclosures of which are incorporated herein by reference. In certain vehicles it is desirable to introduce ventilation through a manually actuated dedicated vent located in a roof or sidewall of the vehicle. These vents open both toward and away from the oncoming flow of air when the vehicle is in motion to introduce and expel air, respectively. The vent may open in stages determined by rest positions along a cam or track that cooperates with guide ends of a tensioning rod to set the position of the vent. The guide ends are biased against the cam or inside the track by the tensioning rod""s cooperation with guide arms mounted on the cover or lid. With detents at intermittent locations on the cam, the vent provides some options for selecting the degree of opening of the vent. However, a by-product of existing cams such as the generally triangular cams is that the vent continues to open at a generally constant rate as the guide ends travel along the cam from the closed to the fully open position. Moreover, there is not a stable and secure receiving recess on the cam surface to ensure that the guide end does not inadvertently move on the cam.
It has been determined by the present inventor that the prior art vents open too wide in some instances, causing a hazard when the vents are disposed on the side of the vehicles. Namely, the vents when open can catch on objects and damage both the vehicle and surrounding objects, or the vent could injure a person standing by the vehicle. Thus, the art would benefit from a vent design that would limit the opening of the vent in comparison with the existing vents.
The present invention provides a two-way vent that comprises a pivoting lid that cooperates with an opening in a frame to selectively open and close the vent. A handle is mounted to the pivoting lid through a connected tensioning rod that rides on a pair of preferably symmetric cams at a pair of rollers on each end. Actuation of the handle causes the lid to pivot about the frame at a forward or rear edge as the rollers travel along the cams"" surfaces. To control the degree of pivoting of the lid, and hence the degree of opening of the vent, the cam surface is selected to have a shape generally comprising an apex on its centerline, and first and second convex sides each terminating respectively in a recess adjacent the base of the cam. The first and second cam surfaces preferably includes a lateral cusp defining a transition from the convex surface to the recess. The recesses provide a stable position for the rollers that makes it unlikely that the roller can be inadvertently displaced due to wind gusts or vibration. Moreover, the degree of opening of the vent as the rollers ride the cam surfaces of the present invention is reduced by the narrowing and shortening of the cam. In a preferred embodiment the convex sides of the cam are circular in profile, and the recesses are circular in profile.